Age-Related Decline in Female Fertility

I cannot stress enough the negative impact of female aging on reproductive outcomes. Every day that I see patients in the clinic, I discuss the importance of the age-related decline in female fertility. I typically describe this as a case of "cruel biology," because for women, unlike for men, the passage of time is a treacherous adversary in terms of achieving a pregnancy and building a family.

For many men, sperm production sufficient to achieve a pregnancy occurs throughout their entire lives, and men have produced pregnancies in their 70s or 80s. A notable example is Charlie Chaplin who fathered five children from the age of 62 to 73. While aging in men does result in a lower number of moving sperm, it does not seem to result in a reduced capacity to fertilize an egg and produce a pregnancy. In a recent study, pregnancy outcomes in donor egg cycles were not reduced with increasing male age (1).

For women, however, the story could not be more different. Many women are surprised to learn that fertility begins to decline in their early 30s and declines even more rapidly after age 37. This fact has been observed across the last four to five centuries (2) and is reflected in the success with IVF at our clinic today.

One of the reasons for this is the decline in the number of eggs resting within the ovaries. Prior to birth, there are approximately 6-7 million eggs in the ovaries. However, at the time of birth, there are only 1 million. By the time of puberty this number has been reduced to 300,000 to 500,000, and by 37 years of age, only 25,000 eggs remain! The natural age-related decline in fertility is accompanied by a significant decrease in the quality of the eggs, resulting in an increased risk of miscarriage.

Not only does reproductive aging affect egg quality, but as age increases, there is a greater risk of other disorders that may have an adverse impact on fertility: fibroids, damage to the Fallopian tubes and endometriosis. Because of the age-related decline in fertility, the increase in the incidence of disorders that impair fertility and the greater risk of pregnancy loss, women older than 35 should undergo evaluation and treatment after six months of failed attempts to conceive.

In the end, the reproductive aging is not an ally in the quest of achieving a pregnancy, and being keenly aware of this will make it more likely that you, too, will achieve a fertile future.